The field of the invention is that of dual fuel powered compression ignition internal combustion engines. More particularly, the field of the present invention is that of a diesel engine which can alternatively or simultaneously be powered by compressed natural gas and a petroleum or non petroleum liquid diesel fuel.
To help clean up the environment, great strides have been made in reducing the exhaust emissions of automotive vehicle engines. In a further attempt to lower vehicle engine emissions, the use of alternative fuels has been explored. An excellent example of such a fuel is compressed natural gas (CNG). There has been much progress in lowering emissions by using CNG, most notably in spark-ignited internal combustion engines.
It is desirable to extend the use of CNG to compression ignition engines such as diesel engines. However, CNG typically must be compressed to far higher pressures than what typically occur in a compression cycle of a conventional diesel engine before the CNG will auto-ignite. Additionally, it is very hard to disperse a gas within a compression chamber under pressurized conditions. Liquids are easier to inject into a pressurized combustion chamber to achieve disbursal of the fuel within the combustion chamber. Accordingly, to utilize CNG, a small amount of diesel fuel is typically added which auto-ignites at the conventional diesel compression pressure. The ignited diesel fuel generates a temperature spike within the combustion chamber which causes the CNG to ignite.
Prior to the present invention, there have been various inventions to allow the use of CNG in diesel engines. One such invention has a coaxial injection of CNG and diesel fuel into the cylinder combustion chamber of the engine. However, the injector utilized for the coaxial injection is technically complex. Furthermore, injectors, which have been brought forth previously for coaxial injection of CNG and diesel fuel, have been very expensive.
It is desirable to provide a diesel engine that can be powered by a mixture of CNG and liquid diesel fuel. It is also desirable to provide a multi-fuel diesel engine which has a less complex design for its injector units. It is furthermore desirable to provide a multi-fuel diesel engine as described wherein the injectors are less expensive than those previously provided.
To make manifest the above delineated and other desires, the revelation of the present invention is brought forth. The present invention provides a CNG/diesel liquid fuel internal combustion engine that uses CNG to bring the diesel fuel out of a dual fuel injector. The dual fuel injector has a mixing chamber with an outlet fluidly connected with the combustion chamber via a first valve. A liquid fuel line is provided for delivering liquid fuel to the mixing chamber. The liquid fuel line is connected to the mixing chamber via a second valve. A combustible gas delivery line is also connected with the mixing chamber to deliver compressed combustible gas thereto. In operation, the second valve is opened to inject pressurized liquid fuel into the mixing chamber. Subsequently, the first valve is opened to allow the CNG to bring the diesel fuel into the combustion chamber.
Accordingly, mechanical power from the engine is needed only for a low pressure diesel fuel (feed) pump ( less than 50 bar), in contrast to a high pressure fuel pump ( greater than 200 bar, up to a few thousand bar) for a conventional diesel engine. Due to the lower power requirement for driving the diesel fuel pump, fuel economy of the engine is improved. The lower pressure diesel fuel pump is also less expensive than the prior required high-pressure diesel fuel feed pump.
It is a feature of the present invention to provide a dual fuel compression ignition diesel engine. It is also a feature of the present invention to provide a dual fuel internal combustion diesel engine which does not require a high-pressure pump for the diesel fuel.
The above-noted features of the present invention will become apparent to those skilled in the art from a review of the invention as it is provided in the accompanying drawings and detailed description.